1. Field of the Invention
This invention relates to a compound transmission comprising a multispeed main transmission section connected in series with a multispeed auxiliary transmission section, preferably of the combined splitter and range type, and to a combined shift control device therefor. In particular, this invention relates to a shift control unit for a manually shifted compound transmission comprising a shift finger operated shift bar housing assembly for selecting mainsection gear ratios, at least one of said mainsection ratios selectable in two different shift bar housing assembly positions, and a control device or switch for sensing positioning of the shift bar housing assembly in said two positions and for automatically shifting a two-speed range portion of said auxiliary transmission (or multispeed axle or multispeed transfer case) accordingly.
2. Description of the Prior Art
Compound transmission systems comprising manually shifted multispeed main transmission sections connected in series with one or more multispeed auxiliary drivetrain sections, usually of the range, splitter or combined range/splitter type are well known in the prior art. The auxiliary sections are usually input and/or output auxiliary transmission sections but may also be multispeed drive axles, transfer cases or the like. Examples of such compound systems may be seen by reference to U.S. Pat. Nos. 4,754,665; 3,648,546; 3,799,002; 4,455,883 and 4,527,446, the disclosures of which are hereby incorporated by reference.
These transmissions, while well received and widely utilized in manually shifted heavy duty vehicles, are not totally satisfactory as a pair of switches, in addition to the shift lever, must be manually manipulated or the double-H control therefor requires extensive transverse shift lever movement.
Control devices or assemblies for controlling the shifting of both the main transmission and the auxiliary drive train unit by requiring the vehicle operator to manipulate only a shift lever along an extended H type shift pattern are also known in the prior art as may be seen by reference to U.S. Pat. Nos. 3,429,202; 4,455,883; 4,561,325 and 4,663,725, the disclosures of which are hereby incorporated by reference.
These prior art controls are not totally satisfactory as extensive shift lever/shift tower modification is required; sensors and/or controls located at the shift tower, and wiring and/or air control lines thereto, is required; relatively complicated structure, such as multiple shift fingers are required, the controls are not easily adapted for both direct and remote control usage and/or an interlock to inhibit, but not prohibit, shifting of the main transmission section until the selected auxiliary range ratio is fully engaged was not provided.